In PS (Packet Switched) communication networks, data is generally communicated between packet network devices, e.g. routers, gateways, etc., in form of data packets according to suitable communication protocols, e.g. IP (Internet Protocol). Between the packet network devices communication links are established, on which the data packets are transmitted.
Traffic engineering is generally known as a process for setting up suitable paths between packet network devices for a given set of transmission demands, along with respective desired traffic volumes. Typically, such a path comprises a plurality of communication links and a number of intermediate packet network devices on the way from a first packet network device to a destination packet network device.
In traffic engineering various processes are applied for controlling establishment of paths between packet network devices via one or more communication links and intermediate packet network devices. One example is to use a connection oriented infrastructure for this purpose, such as MPLS RSVP-TE (Multiprotocol Label Switching, Resource Reservation Protocol-Traffic Engineering). This scheme requires adding new infrastructure to the network, which is not attractive for some of the network operators.
Therefore, many service providers deploy traffic engineering right on top of the traditional routing protocols that already are available in the packet network devices, e.g. OSPF (Open Shortest Path First), defined in “RFC (Request For Comments) 2328”, IETF (Internet Engineering Task Force), or IS-IS (Intermediate System to Intermediate System intra-domain routing information routing information exchange protocol) defined in “ISO/IEC (International Standard Organisation/International Electrotechnical Commission) 10589:2002”, by carefully setting the link costs, such that the paths to be established would be selected by the routing protocol as shortest path.
Throughout this description the term “cost” will be used to represent an administrative value assigned to a link. However, it is to be noted that alternative terms are used within literature to define this value, for instance “weight” or even “length”. The length or cost of a path is the sum of the lengths or costs of the links which constitute the path. It is also to be noted that the link costs in general are not related to the physical lengths of the links, but is merely an administrative parameter to be used to control the routing of paths between packet network devices.
The term “traffic demand” will be used to denote that an amount of packet data would be forwarded from a first packet network device to another packet network device. For instance, one traffic demand may be that a first router in a PS communication network wants to forward an amount of packet data to a second router, and another traffic demand may be that a third router wants to forward another amount of packet data to a fourth router. In general, the packet data networks comprise a plurality of routers or other packet network devices and are connected by communication links or communication paths, and intermediate routers in a network structure. In the packet network devices of a PS communication network, there will typically be more than one traffic demand to take care about when routing/transporting packet data.
The term “load balancing” will be used to denote processes for controlling routing of packet data in PS communication networks, in order to balance the loads of the packet data between communication links or communication paths in the PS communication networks. In general, when routing in accordance with OSPF, load balancing is performed in accordance with ECMP (Equal Cost MultiPath)
When transporting packet data in PS communication networks, routing and transporting of packet data are performed in the IP-layer. The IP-layer comprises a plurality of planes, i.e.; the management plane, where communication links and communication paths are set up or established; the control plane, where packet data is routed on the communication links or communication paths; and the data plane, where the forwarding or transport of the packet data is performed.
With reference to FIG. 1, which is a schematic overview, a shortest path routing scenario for a PS communication network with a plurality of communication links will now be described according to an example.
In a PS communication network 100 a plurality of packet network devices (illustrated as filled dots) are connectable to each other by communication links (lines between the filled dots) which each have respective link costs associated. Between a first packet network device 102 and a second packet network device 104, a plurality of possible paths are available for routing, e.g.: a first path (illustrated with bold arrows) which has a total cost of 2+1+5=8, and a second path (dash dotted arrow) which has a total cost of 3+1+5=9. All the communication network devices in this example route packets in accordance with OSPF, and the first packet network device selects the first path because of its lower cost.
With reference to FIG. 2, which is a schematic network graph, a load balancing scenario for a packet network device A will now be described according to an example.
In a PS communication network, a traffic demand is to forward 3 Gb/s (Gigabit per second) from the packet network device A to the packet network device D. The routing is performed in accordance with the OSPF protocol. In this scenario, the first packet network device A has two possible paths to route, the first communication path which is associated with a desired traffic volume of 1 Gb/s, and the second communication path which is associated with a desired traffic volume of 2 Gb/s.
As stated above, when routing according to OSPF, load balancing is commonly performed according to ECMP. When performing load balancing in accordance with ECMP, the packet data flow will be split equally over the routed communication links, when routing. Here, 1.5 Gb/s will be routed on each of the first communication link AB and the second communication link AC.
In this case 1.5 MB/s will be routed on the first communication link, instead of 1 Mb/s. This overload may cause excessive packet losses, delays, and/or other communication problems when forwarding the packet data. In addition, the higher desired traffic volume of the second communication link will not be fulfilled.
There is a need to effectively control the utilisation of available communication resources for packet data traffic in PS communication networks.